Evaluation of the Mechanochemical Synthesis of ZnO Nanoparticles as a Potential Treatment Technology for Restaurant Wastewater Discharge Within Awka Capital City, Nigeria

The investigation of the mechanochemical synthesis of ZnO nanoparticles as a potential treatment technology for restaurant wastewaster discharge within awka metropolis was conducted. The ZnO nanoparticle synthesized through mechanochemical synthesis had irregular shape with sizes from a few micrometers to tens of micrometers, indicating a powdered sample. The surface between the particles was rough and porous, where EDX analysis revealed the material’s elemental composition, of Silicon (4. 58%), Aluminium (1. 80%), Iron (8. 10%), and others. The turbidity levels for untreated and treated wastewater were 377 mg/L and 52 mg/L, showing an 86% removal rate. The pH of untreated water was 8. 4, while treated water was 7. 11. Concentrations of sulphate, nitrate, and phosphate decreased significantly after treatment. Heavy metals concentration, including cadmium and lead, were reduced, while zinc level increased. The untreated water had a TDS value of 1274. 333 mg/L, while after treatment with zinc oxide, TDS levels dropped to 411. 3333 mg/L. The dissolved oxygen (DO) levels in untreated (22. 7667 mg/L) and treated samples (8. 6 mg/L) were higher than EPA’s permissible limit of 4 mg/L. The untreated wastewater showed a high BOD concentration of 297 mg/L. COD of the untreated samples was 627. 6667 mg which decreased to 139. 6667 mg/L after treatment. Untreated waste water contained higher concentrations of PAHs, which reduced after treatment with zinc oxide. Zinc oxide nanoparticles showed a 66% removal rate of VOCs, with the highest concentrations associated with styrene and n-Propylbenzene. These compounds can be treated with zinc oxide nanoparticles, demonstrating their potential for treating VOCs before discharge into the environment. The study concluded that treatment with zinc oxide nanoparticles effectively improved the quality of wastewater by reducing harmful substances to acceptable levels, thus minimizing environmental and health risks.